The present invention relates generally to an improved scrubber for cleaning streams of gas laden with toxic solid, liquid or gas contaminants. Specifically, this invention relates to a circulating air scrubber.
Scrubbers for cleaning streams of gas, especially air, laden for example with toxic solid particles and with poisons in gas or liquid phase are known in various embodiments. In conventional scrubbers, a cleaning or scrubbing liquid in finely sprayed, vaporized or atomized form in added to the gas stream laden with contaminants. Generally water is used with the addition of an additive, especially one with a chemical absorbing action, such as alcohol, gas solvents, neutralizing substances, and the like.
After thorough mixing, for example by vortexing, the harmful materials are extracted from the laden gas stream, captured in a filter device and/or condensation arrangement, and removed. Disposal of the resulting accumulations of contaminated scrubbing liquid is a substantial problem with conventional devices.
In conventional air scrubbers, the gas is at 100% relative humidity because of the temperature in the condensation region. This can readily be seen from the known Mollier diagram. For example, at normal ambient temperatures, 3 m.sup.3 of scrubbing liquid are needed for each 1,000 m.sup.3 /h or air. In the continuous cleaning of a larger space, for instance, in a chemical plant in which toxic gases or dust particles arise on a larger scale, a correspondingly large quantity of contaminated scrubbing liquid is accumulated for disposal.
Operation of conventional scrubbers with circulating air is expensive because the gas stream to be cleaned must be cooled, in order to ensure condensation of the scrubbing liquid.
Furthermore, conventional air scrubbers can only remove solid materials to a particle size of about 10 to 50 .mu.m. For smaller particle sizes an additional cleaning device is necessary, such as an electrostatically operated active carbon filter.
The object of the present invention is to provide a circulating air scrubber which requires relatively very little scrubbing liquid, is suitable for removal of very small solid particles in the range of 5 .mu.m and below, and is suitable for operation with circulating air.